Improvement in the automatic self-cleaning arrangement of a cooking oven

Abstract: Food cooking oven, comprising an access door (1), a cooking cavity (2), a motor-driven fan (3) situated on the back side of said cooking cavity, a partition wall (4) arranged to diffuse the air flow generated by said fan, a rear chamber (5) situated behind said fan and confined on its front side by said fan and said partition wall (4), and provided with a conduit (6), an end portion of which terminates with a nozzle (7) positioned near the wheel of the fan (3), whereas the other end portion of which is connected with a reservoir (8) comprising a pump (9) adapted to pump the liquid contained in said reservoir into said conduit (6), said pump (9) and said fan (3) being connected to a control device (10) adapted to control their operation, and further provided with a second conduit (17), the outlet end portion of which terminates with a second nozzle (18) that is also arranged close to the fan (3).

Description: The present invention refers to a food cooking oven with fan-assisted operation, which is adapted to perform cooking cavity cleaning automatically. In the following description reference is made in particular to a food cooking oven of the type intended for use in catering operations, professional kitchens and similar applications. It will however be appreciated that what is described and claimed in connection thereto in this patent actually applies to any kind whatsoever of food cooking ovens. It is generally known that, during cooking of foodstuffs in an oven, and especially during fan-assisted operation of such an of oven, the cooking cavity thereof is subject to quick and heavy soiling by splashes of food particles and juice or gravy droplets, as well as, in particular in the case of ovens with fan-assisted operation, due to the effect of conveyance of the air (air-borne soil) that becomes impregnated with emanations from the food being cooked and deposits them onto the walls of the oven cavity. If a sufficiently high temperature is prevailing in the oven cavity, such particles being deposited on the walls thereof become thermally set thereon due to their burning and charring. Such a soiling of the oven cavity is a wholly undesired effect, since it gives rise to a number of well-known drawbacks which are shortly discussed here only for the sake of a better understanding of the problem. First of all, the very presence of food remainders in the oven cavity brings about the possibility of a decay and putrefaction thereof, with obvious risks of a hygienic-sanitary nature resulting therefrom. Furthermore, such food residues deposited onto the oven cavity walls, especially when they are not burned or charred, are generally subject to progressive deterioration as they go through subsequent cooking cycles in the oven cavity, and tend to dissolve by giving off fumes and unpleasant odours. Now, these drawbacks are generally tolerated, albeit to a certain extent, when they relate to cooking ovens used in household applications, where there is no definite obligation set by external authorities governing the way in which oven cavities should be cleaned. However, even there such a problem is being felt to such an extent that the solution consisting of providing the ovens with a so-called self-cleaning feature is widely known to have rapidly expanded in the marketplace. In this case, the ovens are generally provided with plates that are used to clad the walls and are provided with a special pyrolytic coating: upon conclusion of the actual cooking process, the temperature in these ovens is increased to a value of up to approx. 400°C, so that the pyrolytic coating is enabled to "burn off" and dissolve the food residues deposited onto it. Such a solution, however, suffers from a number of drawbacks: first of all it implies a considerable use of energy to boost the temperature inside the cooking cavity to the required, typically high self-cleaning value; furthermore, this self-cleaning process has proven to be just partially effective, since it fails to 'remove' possible soil particles that are not deposited exactly on said pyrolytic plates. A third drawback results from the fact that such self-cleaning plates with pyrolytic coating are typically subject to become exhausted in a relatively quick way, thereby losing their self-cleaning property. The problem of adequately keeping the inside of the oven cavity in a clean state is felt in a particularly acute way in the use of the ovens for cooking foods in catering establishments and professional kitchen in general, where the need for systematically cleaning the cooking cavity arises both from definite requirements set by standard regulations and the fact itself that such ovens are typically subject to a heavy-duty way of utilization, ie. they are used in an intensive way, quite often more times each day throughout the year. It occurs in fact that after each cooking cycle, where a cooking cycle is in this case understood to mean a sequence or a certain number of subsequent cooking processes, the oven operator is bindingly requested to clean the interior of the cooking cavity using a by now standardized method consisting of manually spraying a certain amount of very alkaline detergent substances onto the cavity walls, shutting the oven door and allowing said detergent substances to chemically attack the cooking residues to be removed for an adequately long period of time, which cannot be shorter than approx. 15 minutes, opening again the oven door and manually cleaning the cavity under removal of said residues as decomposed by said substances. These handlings are usually felt as very unpleasant by the oven operators owing to the ill-smelling exhalations and aggressive vapours that are emitted when the oven door is eventually opened to reach inside the cavity for cleaning. Furthermore, the subsequent rinsing phase, due to the fact that it must be performed by hand and generally requires a lot of time to be carried out, tends to make operators unavailable just when full personnel availability is requested in the kitchen for food preparation purposes. The need therefore arises to provide an oven, especially one capable of being used in particular in commercial and institutional catering establishments, which is adapted to perform a fully automatic self-cleaning process in a most simple way, without any involvement whatsoever of the operator, as well as without this implying any need to carry out any significant design and/or construction modifications in the ovens themselves. It is a purpose of the present invention to improve the construction of said cooking ovens by means of the features as substantially described with reference to the appended claims. The invention itself will be more clearly understood on the basis of the description given below merely by way of non-limiting example with reference to the accompanying drawings, in which: Figure 1 is a persepctive view showing schematically a vertical section of a cooking oven according to the state of the art; Figure 2 is a view of a constructional variant of the oven shown in Figure 1 ; but embodying the present invention. Referring to Figure 1, this is shown to illustrate the interior of a food cooking oven as provided in particular for commercial and/or institutional catering applications, and divulged in DE-A-2842771. This oven is shown to comprise an access door 1 for reaching inside the cooking cavity 2, a motor-driven fan (3) located on the back side of said cooking cavity, a partition wall 4 acting as a baffle to divide and convey the air flow generated by said fan, a rear chamber 5 situated behind said fan and confined on its front side by said fan and said partition wall 4. Said oven is in addition provided with a conduit 6, an end portion of which terminates with a nozzle 7 positioned near the wheel of the preferably tangential-type fan 3, whereas the other end portion of which is connected with a reservoir 8 comprising a preferably priming-type pump 9 adapted to pump the liquid contained in said reservoir into said conduit 6. Furthermore, both said pump 9 and said fan 3 are connected with a control arrangement 10 which is adapted to control their energization and de-energization according to criteria that will be explained in a more detailed way farther on. The oven is of course provided with a number of further devices and component parts, which however are substantially irrelevant as far as the actual purpose of this invention is concerned and shall therefore not be dealt with here any further. The principle on which the operation of such an arrangement is based is as follows: at the beginning, the reservoir 8 is filled with a liquid substance that is capable of deterging and dissolving the food residues deposited onto the walls of the cooking cavity; then, through a corresponding command sent to the control device 10, both the pump 9 and the fan 3 are energized and allowed to operate at the same time. Owing to the action of the pump, the liquid contained in the reservoir 8 is pumped through the conduit 6 towards the nozzle 7, from which it is sprayed against the blades of the fan 3, which, due to the fact that it is operating too, is therefore able to generate a turbulent flow which atomizes said liquid and transports it along the whole path covered by said flow when circulated normally, so that it necessarily occurs that it is deposited on those parts of the oven which constitute the conduit through which flows and which delimitates said flow. The duration of the phase in which the detergent substances are in this way delivered to be sprayed by the fan can be pre-determined at will, on the basis of various factors, by simply acting on the control device 10 accordingly. Upon conclusion of such a detergent delivery phase, the actual rinsing phase is then started for final removal of the food residues previously dissolved by the detergent substances. This rinsing phase is carried out by de-energizing the pump 8 and starting the pump 15 which draws from a second reservoir 16 filled with appropriate rinsing liquid, eg. water. Said pump impels the water contained in the reservoir 16 into a second conduit 17, one end portion of which terminates with a second nozzle 18, which is also situated near the fan 3 and is adapted to spray a continuous jet of water against the rotating blades thereof. At this point, owing to the action of the rotating fan wheel, said jet of water undergoes an atomization process, after which it is then carried all along the normal air circulation path in the oven cavity, in a similar way as it occurred in conjunction with the afore described process for the application of the detergent substance. Such a mechanically forced flow of atomized rinsing liquid impinges against the soiled walls, on which however the food residues and the soil in general had been previously dissolved and detached therefrom, and rinse them clean by flushing away said soiling residues towards the bottom of the oven cavity, from where they can then be removed in an automatic way by making use of the outlet opening 28 and the corresponding outlet conduit 29 that are normally already provided in such types of ovens. The operation of the two pumps 9 and 15 and the fan 3 is controlled and synchronized by the control device 10 according to energization and de-energization sequences that can be defined in accordance with the desired results and can be programmed in advance in any of the various ways that are well-known to those skilled in the art. Such a control device can then be actuated by the operator through a simple external control element, such as a button, knob or the like (not shown), eg. located on the control panel of the oven. However the above solution showing the two separate conduits 6 and 17 does suffer the drawback that it may be hindered or prevented by the lack of room in front of and behind the fan. To improve said situation, a cooking oven according to the invention is shown in Figure 2, which illustrates an oven in which the nozzles provided for spraying the detergent substance and the rinsing liquid are joined into a single nozzle 20 coming out from a single conduit 21 which, at a certain point down along its path, divides into two separate branches 22 and 23 leading to the two separate reservoirs for the detergent substance and the rinsing liquid. Furthermore, in order to prevent the single streams of liquid flowing from the two distinct reservoirs from flowing into the reservoir which is not in use at the moment, instead of directing their course towards the common nozzle 20, it is advantageous to provide a respective arrangement 24, 25, such as for instance a check valve or a solenoid valve operated by the same control device 10, on each distinct branch 22, 23 of the conduit. As an alternative solution thereto, a water flow diverter, such as for instance a two-way solenoid valve 26 arranged in correspondence of the branch-off point of the conduit branches 22 and 23, can be provided. A further, advantageous variant to the afore described embodiments consists in doing away with both the reservoir 16 containing the rinsing liquid and the related pump 15, whereas the conduit 17 is connected directly to the water supply mains. In such a way the double advantage of a much simpler construction and an enhanced effectivenes in flushing away the soil residues is obtained, owing to the greater pressure available in the water supply mains with respect to the delivery pressure that can be obtained by the use of a small pump. A further improvement that may be cited here by way of example can be achieved by joining said single nozzle 20 and the related conduit 21 together with the humidifier nozzle and conduit that are usually already provided in such an oven to let water into the cooking cavity during some particular phases of the cooking processes carried out therein.

Claims: Food cooking oven, comprising an access door (1), a cooking cavity (2), a motor-driven fan (3) situated on the back side of said cooking cavity (2), a partition wall (4) provided to diffuse the air flow generated by said fan (3), a chamber (5) accomodating said fan (3) and confined on its front side by said partition wall (4), a first branch (22) being provided with an end portion connected via a pump (9) to a first reservoir (8) adapted to supply detergent substances, a second branch (23) being additionally provided, an end portion of which terminates via a respective pump to a second reservoir, adapted to supply rinsing liquids, the opposite ends of said first and second portions terminating with respective nozzles (7,18), characterized in that said nozzles (7,18) provided for spraying the detergent substance and the rinsing liquid, respectively, are joined together into a single nozzle (20) coming out from a single conduit (21) which is divided into said first and second branches (22,23). Cooking oven according to claim 1, characterized in that said source of said end portion of said second branch (23) is connected to the water supply mains. Cooking oven according to claim 1 or 2 characterized in that there are provided two devices (24,25) on the respective branches (22,23) which are adapted to prevent liquids from flowing towards the respective reservoirs. Cooking oven according to claim 3, characterized in that said devices (24,25) are constitued by check valves or solenoid valves. Cooking oven according to claim 4, characterized in that in correspondence of the point of departure of said branches (22,23) of the conduit there is provided a two-way flow diverter (26). Cooking oven according to any of the preceding claims, characterized in that said single conduit (21) is also used as humidification conduit for letting moisture into the cooking cavity during the cooking process.

Inventors: TOMMASINI STELVIO, TOMMASINI, STELVIO
Applicants: ELECTROLUX ZANUSSI GRANDI IMPI, ELECTROLUX ZANUSSI GRANDI IMPIANTI S.P.A.
Application year: 1994
Main classification: F24C14
IPC codes: F24C15, F24C14